The present invention relates to manufacturing planning systems, and more particularly, to a method of accounting for equipment constraints in a manufacturing planning system.
A typical manufacturing planning system considers data pertaining to fabrication process route, production capacity constraints, material constraints, shop status, work-in-progress (WIP) status, customer orders, priority, and management objectives. In response to these inputs, the planning system outputs manufacturing goals and objectives and other related information including, without limitation, plan finish date, capacity plan, bottleneck equipment identification, scheduling sequence, and production start and finish times. In doing so, the planning system balances demand (customer orders) and supply (WIP) and determines work order sizing if demand is larger than supply.
As is well known in the art, virtually every tool, machine, or other equipment used in a manufacturing process has its own set of operating tolerances. Thus, when multiple, close tolerance processing stages are performed on a lot of material using different tools or machines, critical dimensions of the product may fall outside the allowable limits of the product""s specification, thereby requiring re-work which may negatively impact product yield and productivity.
Hence, the same tool or machine may be assigned to perform close tolerance processing stages. This type of equipment restriction or constraint is typically implemented in daily manufacturing scheduling, but, is not considered in the manufacturing planning system. For this reason, the capacity of the tool or machine is often overestimated by the planning system, which causes the tool or machined to become a bottleneck in the manufacturing process.
Accordingly, a method is needed to account for equipment utilization constraints in a manufacturing planning system
The invention disclosed herein is a method of accounting for manufacturing resource re-entry constraints in a manufacturing planning system. In the method a relationship is built from a manufacturing operation to be rendered on lots of material, to a plurality of manufacturing resources capable of performing the operation. This may be accomplished by assigning a first group of manufacturing resources to the operation which are each capable of performing the operation. A second group manufacturing resources each capable of performing the operation is also assigned to the operation, wherein each of the manufacturing resources of the second group have its re-use in performing the operation on the same lot of material constrained to ones of the lots of material requiring the operation to be performed with close tolerances. For a selected lot of material, any of the manufacturing resources of the first group may be selected for performing the operation if the selected lot of material does not require the operation to be performed with close tolerances. If however, the selected lot of material requires the operation be performed with close tolerances, then a manufacturing resources is selected from the second group of manufacturing resources.